Nonvolatile semiconductor memory device

ABSTRACT

A nonvolatile semiconductor memory device comprises a plurality of memory blocks, each including a plurality of cell units and each configured as a unit of execution of an erase operation. Each of the cell units comprises a memory string, a first transistor, a second transistor, and a diode. The first transistor has one end connected to one end of the memory string. The second transistor is provided between the other end of the memory string and a second line. The diode is provided between the other end of the first transistor and a first line. The diode comprises a second semiconductor layer of a first conductivity type and a third semiconductor layer of a second conductivity type.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. §120 from U.S. Ser. No. 14/094,438 filed Dec. 2, 2013,which is a continuation of Ser. No. 13/870,164 filed Apr. 25, 2013 (nowU.S. Pat. No. 8,659,947 issued Feb. 25, 2014), which is a continuationof U.S. Ser. No. 13/041,579 filed Mar. 7, 2011, and claims the benefitof priority under 35 U.S.C. §119 from Japanese Patent Application No.2010-211326 filed Sep. 21, 2010, the entire contents of each of whichare incorporated herein by reference.

FIELD

Embodiments described in this specification relate to an electricallydata-rewritable nonvolatile semiconductor memory device.

BACKGROUND

In recent years, many semiconductor memory devices having memory cellsdisposed three-dimensionally are proposed in order to increase thedegree of integration of memory. For example, a semiconductor memorydevice employing transistors of a circular cylindrical type structurerepresents one such conventional semiconductor memory device havingmemory cells disposed three-dimensionally.

There is a risk that, when an erase operation is executed on such anabove-described semiconductor memory device, the erase operation is notexecuted accurately due to the leak current flowing into the memorycells from various wirings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a nonvolatile semiconductor memory devicein accordance with a first embodiment.

FIG. 2 is a schematic perspective view of the nonvolatile semiconductormemory device in accordance with the first embodiment.

FIG. 3 is a circuit diagram of a memory cell array 1 in accordance withthe first embodiment.

FIG. 4A is a cross-sectional view of the nonvolatile semiconductormemory device in accordance with the first embodiment.

FIG. 4B is a cross-sectional view of the nonvolatile semiconductormemory device in accordance with the first embodiment.

FIG. 5 is an enlarged view of FIG. 4A.

FIG. 6 is a schematic view of during a first erase operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 7 is a timing chart of during the first erase operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 8A is a schematic view of during a first write operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 8B is a schematic view of during the first write operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 9 is a timing chart of during the first write operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 10 is a schematic view of during a first read operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 11 is a timing chart of during the first read operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 12 is a timing chart of during a second erase operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 13 is a timing chart of during a second write operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 14 is a timing chart of during a second read operation in thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 15 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 16 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 17 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 18 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the firstembodiment.

FIG. 19 is a circuit diagram of a memory cell array 1 in accordance witha second embodiment.

FIG. 20 is a cross-sectional view of a nonvolatile semiconductor memorydevice in accordance with the second embodiment.

FIG. 21 is a schematic view of during an erase operation in thenonvolatile semiconductor memory device in accordance with the secondembodiment.

FIG. 22 is a timing chart of during the erase operation in thenonvolatile semiconductor memory device in accordance with the secondembodiment.

FIG. 23A is a schematic view of during a write operation in thenonvolatile semiconductor memory device in accordance with the secondembodiment.

FIG. 23B is a schematic view of during the write operation in thenonvolatile semiconductor memory device in accordance with the secondembodiment.

FIG. 24 is a timing chart of during the write operation in thenonvolatile semiconductor memory device in accordance with the secondembodiment.

FIG. 25 is a cross-sectional view of a nonvolatile semiconductor memorydevice in accordance with a third embodiment.

FIG. 26 is a cross-sectional view of a nonvolatile semiconductor memorydevice in accordance with a fourth embodiment.

FIG. 27 is a cross-sectional view of a nonvolatile semiconductor memorydevice in accordance with a fifth embodiment.

FIG. 28 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the fifthembodiment.

FIG. 29 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the fifthembodiment.

FIG. 30 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the fifthembodiment.

FIG. 31 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the fifthembodiment.

FIG. 32 is a cross-sectional view showing a manufacturing process of thenonvolatile semiconductor memory device in accordance with the fifthembodiment.

DETAILED DESCRIPTION

A nonvolatile semiconductor memory device in accordance with anembodiment comprises a plurality of memory blocks, a first line, asecond line, and a control circuit. Each of the plurality of memoryblocks includes a plurality of cell units and is configured as asmallest unit of an erase operation. The first line is provided commonlyto the plurality of memory blocks and is connected to one ends of theplurality of cell units. The second line is connected to the other endsof the plurality of cell units. The control circuit is configured tocontrol a voltage applied to the plurality of memory blocks. Each of theplurality of cell units comprises a memory string, a first transistor, asecond transistor, and a diode. The memory string is configured by aplurality of memory transistors connected in series, the memorytransistors being electrically rewritable. The first transistor has oneend connected to one end of the memory string. The second transistor isprovided between the other end of the memory string and the second line.The diode is provided between the first transistor and the first lineand has a forward bias direction from a side of the first transistor toa side of the first line. The memory string comprises a firstsemiconductor layer, a charge storage layer, and a first conductivelayer. The first semiconductor layer includes a columnar portionextending in a perpendicular direction with respect to a substrate andis configured to function as a body of the memory transistors. Thecharge storage layer is formed to surround a side surface of thecolumnar portion and is configured to be capable of storing a charge.The first conductive layer is formed commonly in the plurality of memoryblocks to surround the side surface of the columnar portion with thecharge storage layer interposed therebetween and is configured tofunction as a gate of the memory transistors. The diode comprises asecond semiconductor layer and a third semiconductor layer. The secondsemiconductor layer is configured as a first conductivity type extendingin the perpendicular direction with respect to the substrate. The thirdsemiconductor layer is configured as a second conductivity type being incontact with an upper surface of the second semiconductor layer andextending in the perpendicular direction with respect to the substrate.The control circuit is configured to perform the erase operation in aselected one of the memory blocks by setting a voltage of the first linehigher than a voltage of a gate of the first transistor by a firstvoltage to generate a GIDL current for raising a voltage of the body ofthe memory transistors, and setting a voltage of the gate of the memorytransistors lower than the voltage of the body of the memory transistorsby a second voltage. On the other hand, the control circuit isconfigured to prohibit the erase operation in an unselected one of thememory blocks by setting a voltage difference between the voltage of thefirst line and the voltage of the gate of the first transistor to athird voltage different from the first voltage for prohibitinggeneration of the GIDL current.

A nonvolatile semiconductor memory device in accordance with anotherembodiment comprises a plurality of memory blocks, a first line, asecond line, and a control circuit. Each of the memory blocks isconfigured as an arrangement of a plurality of cell units and isconfigured as a smallest unit of an erase operation. The first line isprovided commonly to the plurality of memory blocks and is connected toone ends of the plurality of cell units. The second line is connected tothe other ends of the plurality of cell units. The control circuit isconfigured to control a voltage applied to the plurality of memoryblocks. Each of the plurality of cell units comprises a memory string, afirst transistor, a second transistor, and a diode. The memory string isconfigured by a plurality of memory transistors connected in series, thememory transistors being electrically rewritable. The first transistorhas one end connected to one end of the memory string. The secondtransistor is provided between the other end of the memory string andthe second line. The diode is provided between the first transistor andthe first line and has a forward bias direction from a side of the firstline to a side of the first transistor. The memory string comprises afirst semiconductor layer, a charge storage layer, and a firstconductive layer. The first semiconductor layer includes a columnarportion extending in a perpendicular direction with respect to asubstrate and is configured to function as a body of the memorytransistors. The charge storage layer is formed to surround a sidesurface of the columnar portion and is configured to be capable ofstoring a charge. The first conductive layer is formed commonly in theplurality of memory blocks to surround the side surface of the columnarportion with the charge storage layer interposed therebetween and isconfigured to function as a gate of the memory transistors. The diodecomprises a second semiconductor layer and a third semiconductor layer.The second semiconductor layer is configured as a first conductivitytype extending in the perpendicular direction with respect to thesubstrate. The third semiconductor layer is configured as a secondconductivity type being in contact with the second semiconductor layerand extending in the perpendicular direction with respect to thesubstrate. The control circuit is configured to perform the eraseoperation in a selected one of the memory blocks by setting a voltage ofthe second line higher than a voltage of a gate of the second transistorby a first voltage to generate a GIDL current for raising a voltage ofthe body of the memory transistors, and setting a voltage of the gate ofthe memory transistors lower than the voltage of the body of the memorytransistors by a second voltage. On the other hand, the control circuitis configured to prohibit the erase operation in an unselected one ofthe memory blocks by setting a voltage difference between the voltage ofthe second line and the voltage of the gate of the second transistor toa third voltage different from the first voltage for prohibitinggeneration of the GIDL current.

Next, embodiments of a nonvolatile semiconductor memory device aredescribed with reference to the drawings.

First Embodiment Configuration

First, a configuration of a nonvolatile semiconductor memory device inaccordance with a first embodiment is described with reference to FIGS.1 and 2. FIG. 1 is a block diagram of the nonvolatile semiconductormemory device in accordance with the first embodiment of the presentinvention, and FIG. 2 is a schematic perspective view of the nonvolatilesemiconductor memory device in accordance with the first embodiment ofthe present invention.

The nonvolatile semiconductor memory device in accordance with the firstembodiment includes a memory cell array 1 and a control circuit 1A, asshown in FIG. 1.

The memory cell array 1 is configured by memory transistors MTr1-MTr4arranged in a three-dimensional matrix, each of the memory transistorsbeing configured to store data electrically, as shown in FIG. 2. Thatis, the memory transistors MTr1-MTr4, in addition to being arranged in amatrix in a horizontal direction, are arranged also in a stackingdirection (perpendicular direction with respect to a substrate).

A plurality of the memory transistors MTr1-MTr4 aligned in the stackingdirection are connected in series to configure a publicly known memorystring MS (NAND string). Changing an amount of charge stored in a chargestorage layer of the memory transistors MTr1-MTr4 causes a thresholdvoltage of the memory transistors MTr1-MTr4 to change. Changing thethreshold voltage causes data retained in the memory transistorsMTr1-MTr4 to be rewritten. Connected respectively one each to the twoends of the memory string MS are a drain side select transistor SDTr anda source side select transistor SSTr which are turned on when the memorystring MS is selected. Moreover, the drain side select transistor SDTrhas its drain connected via a diode DI to a bit line BL, and the sourceside select transistor SSTr has its source connected to a source lineSL. Note that specific circuit configurations and stacking structure ofthe memory cell array 1 are described later.

The control circuit 1A is configured to control a voltage applied to thememory cell array 1 (memory block BK to be described later). The controlcircuit 1A comprises row decoders 2 and 3, a sense amplifier 4, a columndecoder 5, and a control signal generating unit (high voltage generatingunit) 6. The row decoders 2 and 3 decode downloaded block addresssignals and so on to control the memory cell array 1. The senseamplifier 4 reads data from the memory cell array 1. The column decoder5 decodes a column address signal to control the sense amplifier 4. Thecontrol signal generating unit 6 boosts a reference voltage to generatea high voltage required during write and erase, and, moreover, generatesa control signal to control the row decoders 2 and 3, the senseamplifier 4, and the column decoder 5.

Next, a circuit configuration of the memory cell array 1 is describedwith reference to FIG. 3. As shown in FIG. 3, the memory cell array 1includes a plurality of memory blocks BK_1, BK_2, . . . , BK_n, aplurality of bit lines BL1, BL2, . . . , BLn, and a plurality of sourcelines SL1, SL2, . . . , SLn. Note that memory blocks are sometimescollectively referred to as memory block BK, instead of specifyingeither one of BK_1, BK_2, . . . , BK_n. Bit lines are sometimescollectively referred to as bit line BL, instead of specifying eitherone of BL1, BL2, . . . , BLn. Source lines are sometimes collectivelyreferred to as source line SL, instead of specifying either one of SL1,SL2, . . . , SLn.

Each of the memory blocks BK includes a plurality of cell units MU andis configured as a smallest unit of an erase operation for erasing data.Each of the bit lines BL is provided commonly to the memory blocks BK_1,BK_2, . . . , BK_n. Each of the bit lines BL is connected to drains of aplurality of the cell units MU. Each of the source lines SL is provideddivided on a memory block BK basis. Each of the source lines SL isconnected commonly to sources of a plurality of cell units MU in onememory block BK.

In the example shown in FIG. 3, each one of the memory blocks BK has thecell units MU provided in a matrix over k rows and n columns. Each ofthe cell units MU includes the memory string MS, the drain side selecttransistor SDTr, the source side select transistor SSTr, and the diodeDI. The memory string MS is configured by the memory transistorsMTr1-MTr4 connected in series. The drain side select transistor SDTr isconnected to a drain of the memory string MS (drain of the memorytransistor MTr4). The source side select transistor SSTr is connected toa source of the memory string MS (source of the memory transistor MTr1).Note that the memory string MS may be configured by more than fourmemory transistors.

As shown in FIG. 3, the memory transistors MTr1 arranged in a matrix inthe plurality of memory blocks BK have their gates connected commonly toa word line WL1. Similarly, the memory transistors MTr2-MTr4 have theirgates commonly connected to word lines WL2-WL4, respectively.

As shown in FIG. 3, the drain side select transistors SDTr arranged in aline in a row direction in the memory block BK_1 have their gatesconnected commonly to one drain side select gate line SGD1,1 (or SGD1,2,. . . , SGD1,k). Similarly, the drain side select transistors SDTrarranged in a line in the row direction in the memory block BK_2 havetheir gates connected commonly to one drain side select gate line SGD2,1(or SGD2,2, . . . , SGD2,k). The drain side select transistors SDTrarranged in a line in the row direction in the memory block BK_n havetheir gates connected commonly to one drain side select gate line SGDn,1(or SGDn,2, . . . , SGDn,k). Note that drain side select gate lines aresometimes collectively referred to as drain side select gate lines SGD,instead of specifying either one of SGD1,1, . . . , SGDn,k. The drainside select gate lines SGD are each provided to extend in the rowdirection and having a certain pitch in a column direction.

In addition, the drain side select transistors SDTr arranged in a linein the column direction have their other ends connected commonly via arespective diode DI to one bit line BL1 (or BL2, . . . , BLn). The diodeDI is provided to have a forward bias direction from a side of the drainside select transistor SDTr to a side of the bit line BL. The bit lineBL is formed to extend in the column direction straddling the memoryblocks BK.

As shown in FIG. 3, the source side select transistors SSTr arranged ina line in the row direction in the memory block BK_1 have their gatesconnected commonly to one source side select gate line SGS1,1 (orSGS1,2, . . . , SGS1,k). Similarly, the source side select transistorsSSTr arranged in a line in the row direction in the memory block BK_2have their gates connected commonly to one source side select gate lineSGS2,1 (or SGS2,2, . . . , SGS2,k). The source side select transistorsSSTr arranged in a line in the row direction in the memory block BK_nhave their gates connected commonly to one source side select gate lineSGSn,1 (or SGSn,2, . . . , SGSn,k). Note that source side select gatelines are sometimes collectively referred to as source side select gatelines SGS, instead of specifying either one of SGS1,1, . . . , SGSn,k.The source side select gate lines SGS are each provided to extend in therow direction and having a certain pitch in the column direction.

In addition, all the source side select transistors SSTr in the memoryblock BK_1 are connected commonly to one source line SL1. Similarly, allthe source side select transistors SSTr in the memory block BK_2 areconnected commonly to one source line SL2, and all the source sideselect transistors SSTr in the memory block BK_n are connected commonlyto one source line SLn.

The above-described circuit configuration of the nonvolatilesemiconductor memory device is realized by a stacking structure shown inFIGS. 4A and 4B. As shown in FIGS. 4A and 4B, the nonvolatilesemiconductor memory device in accordance with the first embodimentincludes a semiconductor substrate 10, and, stacked sequentially on thesemiconductor substrate 10, a source side select transistor layer 20, amemory transistor layer 30, a drain side select transistor layer 40, adiode layer 50, and a wiring layer 60.

The semiconductor substrate 10 functions as the source line SL. Thesource side select transistor layer 20 functions as the source sideselect transistor SSTr. The memory transistor layer 30 functions as thememory string MS (memory transistors MTr1-MTr4). The drain side selecttransistor layer 40 functions as the drain side select transistor SDTr.The diode layer 50 functions as the diode DI. The wiring layer 60functions as the bit line BL and as various other wirings.

The semiconductor substrate 10 includes a diffusion layer 11 in itsupper surface, as shown in FIGS. 4A and 4B. The diffusion layer 11functions as the source line SL. The diffusion layer 11 is divided on amemory block BK basis.

The source side select transistor layer 20 includes a source sideconductive layer 21 disposed on the semiconductor substrate 10 via aninsulating layer, as shown in FIGS. 4A and 4B. The source sideconductive layer 21 functions as the gate of the source side selecttransistor SSTr and as the source side select gate line SGS. The sourceside conductive layer 21 is formed in stripes in each of the memoryblocks MB, the stripes extending in the row direction and having acertain pitch in the column direction. The source side conductive layer21 is configured by polysilicon (poly-Si).

In addition, as shown in FIGS. 4A and 4B, the source side selecttransistor layer 20 includes a source side hole 22. The source side hole22 is formed to penetrate the source side conductive layer 21. Thesource side holes 22 are formed in a matrix in the row direction and thecolumn direction.

Moreover, as shown in FIGS. 4A and 4B, the source side select transistorlayer 20 includes a source side gate insulating layer 23 and a sourceside columnar semiconductor layer 24. The source side columnarsemiconductor layer 24 functions as a body (channel) of the source sideselect transistor SSTr.

The source side gate insulating layer 23 is formed with a certainthickness on a side wall of the source side hole 22. The source sidecolumnar semiconductor layer 24 is formed to be in contact with a sidesurface of the source side gate insulating layer 23 and to fill thesource side hole 22. The source side columnar semiconductor layer 24 isformed in a column shape extending in the stacking direction(perpendicular direction with respect to the semiconductor substrate10). The source side columnar semiconductor layer 24 is formed on thediffusion layer 11. The source side gate insulating layer 23 isconfigured by silicon oxide (SiO₂). The source side columnarsemiconductor layer 24 is configured by polysilicon (poly-Si).

Expressing the above-described configuration of the source side selecttransistor layer 20 in other words, the source side conductive layer 21is formed to surround the source side columnar semiconductor layer 24with the source side gate insulating layer 23 interposed therebetween.

The memory transistor layer 30 includes word line conductive layers 31a-31 d stacked sequentially on the source side select transistor layer20 with insulating layers interposed therebetween, as shown in FIGS. 4Aand 4B. The word line conductive layers 31 a-31 d function,respectively, as the gates of the memory transistors MTr1-MTr4 and asthe word lines WL1-WL4.

The word line conductive layers 31 a-31 d are formed to extendtwo-dimensionally in the row direction and the column direction (in aplate-like shape) over the plurality of memory blocks BK. The word lineconductive layers 31 a-31 d are configured by polysilicon (poly-Si).

In addition, as shown in FIGS. 4A and 4B, the memory transistor layer 30includes a memory hole 32. The memory hole 32 is formed to penetrate theword line conductive layers 31 a-31 d. The memory holes 32 are formed ina matrix in the row direction and the column direction. The memory hole32 is formed at a position aligning with the source side hole 22.

Further, as shown in FIGS. 4A and 4B, the memory transistor layer 30includes a memory gate insulating layer 33 and a memory columnarsemiconductor layer 34. The memory columnar semiconductor layer 34functions as a body (channel) of the memory transistors MTr1-MTr4.

The memory gate insulating layer 33 is formed with a certain thicknesson a side wall of the memory hole 32. The memory columnar semiconductorlayer 34 is formed to be in contact with a side surface of the memorygate insulating layer 33 and to fill the memory hole 32. The memorycolumnar semiconductor layer 34 is formed in a column shape extending inthe stacking direction. The memory columnar semiconductor layer 34 isformed having its lower surface in contact with an upper surface of thesource side columnar semiconductor layer 24.

A configuration of the memory gate insulating layer 33 is now describedin detail with reference to FIG. 5. FIG. 5 is an enlarged view of FIG.4A. The memory gate insulating layer 33 includes, from a side surface ofthe memory hole 32 side to a memory columnar semiconductor layer 34side, a block insulating layer 33 a, a charge storage layer 33 b, and atunnel insulating layer 33 c. The charge storage layer 33 b isconfigured to be capable of storing a charge.

As shown in FIG. 5, the block insulating layer 33 a is formed with acertain thickness on a side wall of the memory hole 32. The chargestorage layer 33 b is formed with a certain thickness on a side wall ofthe block insulating layer 33 a. The tunnel insulating layer 33 c isformed with a certain thickness on a side wall of the charge storagelayer 33 b. The block insulating layer 33 a and the tunnel insulatinglayer 33 c are configured by silicon oxide (SiO₂). The charge storagelayer 33 b is configured by silicon nitride (SiN). The memory columnarsemiconductor layer 34 is configured by polysilicon (poly-Si).

Expressing the above-described configuration of the memory transistorlayer 30 in other words, the word line conductive layers 31 a-31 d areformed to surround the memory columnar semiconductor layer 34 with thememory gate insulating layer 33 interposed therebetween.

The drain side select transistor layer 40 includes a drain sideconductive layer 41, as shown in FIGS. 4A and 4B. The drain sideconductive layer 41 functions as the gate of the drain side selecttransistor SDTr and as the drain side select gate line SGD.

The drain side conductive layer 41 is stacked on the memory transistorlayer 30 via an insulating layer. The drain side conductive layer 41 isformed directly above the memory columnar semiconductor layer 34. Thedrain side conductive layer 41 is formed in stripes in each of thememory blocks BK, the stripes extending in the row direction and havinga certain pitch in the column direction. The drain side conductive layer41 is configured by, for example, polysilicon (poly-Si).

In addition, as shown in FIGS. 4A and 4B, the drain side selecttransistor layer 40 includes a drain side hole 42. The drain side hole42 is formed to penetrate the drain side conductive layer 41. The drainside holes 42 are formed in a matrix in the row direction and the columndirection. The drain side hole 42 is formed at a position aligning withthe memory hole 32.

Further, as shown in FIGS. 4A and 4B, the drain side select transistorlayer 40 includes a drain side gate insulating layer 43 and a drain sidecolumnar semiconductor layer 44. The drain side columnar semiconductorlayer 44 functions as a body (channel) of the drain side selecttransistor SDTr.

The drain side gate insulating layer 43 is formed with a certainthickness on a side wall of the drain side hole 42. The drain sidecolumnar semiconductor layer 44 is formed to be in contact with thedrain side gate insulating layer 43 and to fill the drain side hole 42.The drain side columnar semiconductor layer 44 is formed in a columnshape to extend in the stacking direction. The drain side columnarsemiconductor layer 44 is formed having its lower surface in contactwith an upper surface of the memory columnar semiconductor layer 34. Thedrain side gate insulating layer 43 is configured by silicon oxide(SiO₂). The drain side columnar semiconductor layer 44 is configured bypolysilicon (poly-Si). Moreover, the drain side columnar semiconductorlayer 44 has its lower portion 44 a configured by an intrinsicsemiconductor and its upper portion 44 b configured by an N+ typesemiconductor.

Expressing the above-described configuration of the drain side selecttransistor layer 40 in other words, the drain side conductive layer 41is formed to surround the drain side columnar semiconductor layer 44with the drain side gate insulating layer 43 interposed therebetween.

The diode layer 50 includes an ohmic contact layer 51, a P typesemiconductor layer 52, and an N type semiconductor layer 53, as shownin FIGS. 4A and 4B. The ohmic contact layer 51 causes ohmic contactbetween the P type semiconductor layer 52 and the drain side columnarsemiconductor layer 44. The P type semiconductor layer 52 and the N typesemiconductor layer 53 function as the diode DI.

The ohmic contact layer 51 is formed in a column shape extending in thestacking direction from an upper surface of the drain side columnarsemiconductor layer 44. The P type semiconductor layer 52 is formed in acolumn shape extending in the stacking direction from an upper surfaceof the ohmic contact layer 51. The N type semiconductor layer 53 isformed in a column shape extending in the stacking direction from anupper surface of the P type semiconductor layer 52. The P typesemiconductor layer 52 is configured by polysilicon doped with a P typeimpurity. The N type semiconductor layer 53 is configured by polysilicondoped with an N type impurity.

The wiring layer 60 includes a bit layer 61, as shown in FIGS. 4A and4B. The bit layer 61 functions as the bit line BL.

The bit layer 61 is formed to be in contact with an upper surface of theN type semiconductor layer 53. The bit layer 61 is formed to extend inthe column direction and having a certain pitch in the row direction.The bit layer 61 is configured by a metal such as tungsten.

First Erase Operation

Next, a first erase operation in the nonvolatile semiconductor memorydevice in accordance with the first embodiment is described withreference to FIG. 6.

In the example shown in FIG. 6, memory block BK_1 is assumed to beselected as object of the erase operation. On the other hand, memoryblock BK_2, which shares bit lines BL with memory block BK_1, is not anobject of the erase operation, and erase of data retained in memoryblock BK_2 is prohibited.

During the erase operation, a voltage Vera (for example, about 17 V) isapplied to bit line BL1. In selected memory block BK_1, source line SL1is applied with voltage Vera, and drain side select gate lines SGD andsource side select gate lines SGS are applied with a voltage Vera-ΔVthat is smaller than voltage Vera by ΔV (for example, about 3 V). On theother hand, in unselected memory block BK_2, source line SL2 is appliedwith 0 V, and drain side select gate lines SGD and source side selectgate lines SGS are applied, respectively, with 0 V and a power supplyvoltage Vdd (=1.2 V).

Specifically, as shown in FIG. 6, in selected memory block BK_1, voltageVera of bit line BL1 is higher than voltage Vera-ΔV of gates of drainside select transistors SDTr by an the voltage ΔV. In addition, voltageVera of source line SL1 is higher than voltage Vera-ΔV of gates ofsource side select transistors SSTr by the voltage ΔV. This causes aGIDL current (refer to symbol “E11”) to occur proximal to gates ofsource side select transistors SSTr and drain side select transistorsSDTr in memory block BK_1. Moreover, in memory block BK_1, holes causedby the GIDL current flow into the body of memory transistors MTr1-MTr4,causing a voltage of the body of memory transistors MTr1-MTr4 to rise.

Subsequently, a voltage of the gates of the memory transistors MTr1-MTr4is set to 0 V, in other words, is set lower than the voltage of the bodyof memory transistors MTr1-MTr4. As a result, a high voltage is appliedto the charge storage layer of memory transistors MTr1-MTr4, whereby theerase operation on memory block BK_1 is executed.

On the other hand, in memory block BK_2, a voltage of gates of the drainside select transistors SDTr is set to 0 V. That is, a voltage Vera ofbit line BL1 is set higher than a voltage (0 V) of gates of the drainside select transistors SDTr by Vera. In addition, source line SL2 isset to 0 V, a voltage of gates of the source side select transistorsSSTr is set to the power supply voltage Vdd (for example, 1.2 V). Thatis, a voltage (Vdd) of gates of the source side select transistors SSTris set higher than a voltage (0 V) of source line SL2 by Vera. As aresult, occurrence of the GIDL current is prohibited, and the sourceside select transistors SSTr are turned on.

Now, gates of the memory transistors MTr1-MTr4 are connected commonlybetween memory blocks BK_1 and BK_2 by the word lines WL1-WL4. As aresult, gates of memory transistors MTr1-MTr4 have their voltage set to0 V in memory block BK_2 as well as in memory block BK_1.

However, in memory block BK_2, the voltage of the body of memorytransistors MTr1-MTr4 is not boosted by the GIDL current. Moreover, inmemory block BK_2, the source side select transistors SSTr are turnedon, hence, even if the voltage of the body of memory transistorsMTr1-MTr4 rises due to effects of leak current and so on, that voltageis discharged to source line SL2 via those turned-on source side selecttransistors SSTr (refer to symbol “E12”).

Furthermore, the first embodiment includes the diode DI. This maysuppress a current flowing from bit line BL1 into the body of memorytransistors MTr1-MTr4 in unselected memory block BK_2 (refer to symbol“E13”).

As is clear from the above, in memory block BK_2, the voltage of thebody of memory transistors MTr1-MTr4 is retained at low voltage. As aresult, a high voltage is not applied to the charge storage layer inthose memory transistors MTr1-MTr4, hence, the first embodiment maysuppress incorrect erase in unselected memory block BK_2.

A specific operation procedure when executing the above-described eraseoperation is described with reference to a timing chart in FIG. 7.First, at time t11 in FIG. 7, the voltage of bit line BL1 and voltage ofsource line SL1 are raised to erase voltage Vera (for example, 17 V).Additionally, at time t11, the voltage of source side select gate linesSGS1,1-SGS1,k and voltage of drain side select gate lines SGD1,1-SGD1,kare raised to voltage Vera-ΔV (for example, 14 V). This causes the GIDLcurrent to occur in memory block BK_1.

On the other hand, at time t11, the voltage of source line SL2 ismaintained at 0 V. Additionally, at time t11, the voltage of source sideselect gate lines SGS2,1-SGS2,k is raised to the power supply voltageVdd, and the voltage of drain side select gate lines SGD2,1-SGD2,k ismaintained at 0 V. As a result, the GIDL current does not occur inmemory block BK_2, and the source side select transistors SSTr areturned on.

Next, at time t12, the voltage of word lines WL1-WL4 is lowered to 0 V.This causes data in the memory transistors MTr1-MTr4 in memory blockBK_1 to be erased, and data in the memory transistors MTr1-MTr4 inmemory block BK_2 to be retained (not erased).

First Write Operation

Next, a first write operation in the nonvolatile semiconductor memorydevice in accordance with the first embodiment is described withreference to FIGS. 8A and 8B.

In FIGS. 8A and 8B, an example is described of the case in which a cellunit MU (hereafter referred to as selected cell unit sMU) in memoryblock BK_1 is selected as write target. Description proceeds assumingwrite to be performed on memory transistor MTr3 (hereafter referred toas selected memory transistor sMTr3) in the selected cell unit sMU.

Specifically, as shown in FIG. 8A, in the case of writing “0” data toselected memory transistor sMTr3, the voltage of bit line BL1 is set to0 V. In contrast, in the case of retaining “1” data in selected memorytransistor sMTr3, the voltage of bit line BL1 is set to the power supplyvoltage Vdd (=1.2 V). Source lines SL1 and SL2 are set to the powersupply voltage Vdd.

Then, the memory transistors MTr1-MTr4 included in memory blocks BK_1and BK_2 are applied with a pass voltage Vpass (for example, 10 V) attheir gates and turned on. The source side select transistors SSTr areapplied with a voltage Vdd+Vt at their gates and turned on. This causesthe voltage of the body of the memory transistors MTr1-MTr4 included inmemory blocks BK_1 and BK_2 to be charged to the power supply voltageVdd via source lines SL1 and SL2 (refer to symbol “W11”). That is, thevoltage of the body of the memory transistors MTr1-MTr4 included inmemory blocks BK_1 and BK_2 is set to not less than the power supplyvoltage Vdd that may be applied to bit line BL1 during the writeoperation. Moreover, after a certain time, the source side selecttransistors SSTr are turned off again.

Subsequently, as shown in FIG. 8B, the drain side select transistorsSDTr included in selected cell unit sMU are supplied with voltage Vdd+Vtat their gates. In the case that 0 V is supplied to bit line BL1 towrite “0” data, the drain side select transistors SDTr are turned on,whereby the voltage of the body of the memory transistors MTr1-MTr4included in selected cell unit sMU are discharged to the same 0 V as bitline BL1 (refer to symbol “W12”). On the other hand, in the case thatthe power supply voltage Vdd is supplied to bit line BL1 to retain “1”data, the drain side select transistors SDTr remain turned off, hence,the body of the memory transistors MTr1-MTr4 included in selected cellunit sMU is not discharged but set to a floating state, whereby itspotential is retained at the power supply voltage Vdd.

Then, a voltage of the gate of selected memory transistor sMTr3 is setto a program voltage Vprg (=18 V). As a result, when writing “0” data,the voltage of the body of selected memory transistor sMTr3 isdischarged to 0 V, hence, a high voltage is applied to the chargestorage layer of selected memory transistor sMTr3, whereby the writeoperation on selected memory transistor sMTr3 is executed. On the otherhand, when retaining “1” data, the body of selected memory transistorsMTr3 is set to the floating state and its potential retained at thepower supply voltage Vdd, hence a high voltage is not applied to thecharge storage layer of selected memory transistor sMTr3, whereby thewrite operation on selected memory transistor sMTr3 is not executed.

Now, gates of the memory transistors MTr1-MTr4 are connected commonly bythe word lines WL1-WL4 over a plurality of the cell units MU. If thevoltage of the gate of selected memory transistor sMTr3 is set to theprogram voltage Vprg, the gates of memory transistors MTr3 included inunselected cell units MU are also applied with the program voltage Vprg.However, the voltage of the body of memory transistors MTr1-MTr4included in unselected cell units MU is set to the floating state by theturned-off drain side select transistors SDTr and source side selecttransistors SSTr. As a result, a high voltage is not applied to thecharge storage layer of memory transistors MTr3 included in unselectedcell units MU, whereby the write operation is not executed on thosememory transistors.

A specific operation procedure when executing the above-described writeoperation is described with reference to a timing chart in FIG. 9.First, at time t21 in FIG. 9, the voltage of source lines SL1 and SL2 israised to the power supply voltage Vdd, and the voltage of source sideselect gate lines SGS1,1-SGS1,k and SGS2,1-SGS2,k is raised to voltageVdd+Vt. Additionally, at time t21, the voltage of word lines WL1-WL4 israised to the pass voltage Vpass. This causes the source side selecttransistors SSTr in memory block BK_1 to be turned on, whereby thevoltage of the body of memory transistors MTr1-MTr4 attains the powersupply voltage Vdd. Further, at time t21, bit line BL1 is lowered to 0 Vduring a “0” data write, and is raised to the power supply voltage Vddduring a “1” data retention.

Next, at time t22, the voltage of source side select gate linesSGS1,1-SGS1,k and SGS2,1-SGS2,k is lowered to 0 V. This causes thesource side select transistors SSTr in memory block BK_1 to be turnedoff.

Subsequently, at time t23, the voltage of drain side select gate lineSGD1,2 is raised to voltage Vdd+Vt. This causes the drain side selecttransistor SDTr in selected cell unit sMU only to be turned on.

Next, at time t24, the voltage of word line WL3 is raised to programvoltage Vprog (for example, 18 V). This causes the write operation onselected memory transistor sMTr3 to be executed.

First Read Operation

Next, a first read operation in the nonvolatile semiconductor memorydevice in accordance with the first embodiment is described withreference to FIG. 10. In the example shown in FIG. 10, the readoperation is executed on selected memory transistor sMTr3.

Specifically, as shown in FIG. 10, bit line BL1 is set to 0 V. Sourceline SL1 is set to power supply voltage Vdd, and source line SL2 is setto 0 V. The drain side select transistors SDTr and source side selecttransistors SSTr included in selected cell unit sMU is applied withvoltage Vdd+Vt from the select gate lines SGD1,2 and SGS1,2, and areturned on. Moreover, the gates of memory transistors MTr1, MTr2, andMTr4 are applied with pass voltage Vpass, and the gates of memorytransistors MTr3 are applied with a read voltage Vread (Vread<Vpass). Asa result, in the case that selected memory transistor sMTr3 is retaining“1” data, a current flows from source line SL1 to bit line BL1 (refer tosymbol “R1”), whereby bit line BL1 is charged to power supply voltageVdd. On the other hand, in the case that selected memory transistorsMTr3 is retaining “0” data (in the case that a threshold value ishigh), a current does not flow from source line SL1 to bit line BL1(refer to symbol “R2”), whereby bit line BL1 is not charged but retains0 V. Further, detection of the voltage of bit line BL1 is performed,whereby the read operation on selected memory transistor sMTr3 isexecuted.

A specific operation procedure when executing the above-described readoperation is described with reference to a timing chart in FIG. 11.First, at time t31 in FIG. 11, the voltage of source line SL1 is raisedto the power supply voltage Vdd, and the voltage of source side selectgate line SGS1,2 and voltage of drain side select gate line SGD1,2 areraised to voltage Vdd+Vt. Additionally, at time t31, the voltage of wordlines WL1, WL2, and WL4 is raised to the pass voltage Vpass. This causesthe memory transistors MTr1,2,4, source side select transistors SSTr,and drain side select transistors SDTr to be turned on.

Next, at time t32, the voltage of word line WL3 is raised to the readvoltage Vread. Subsequently, detection of the voltage of bit line BL1 isperformed, whereby the read operation on selected memory transistorsMTr3 is executed.

Second Erase Operation

Next, a second erase operation in the nonvolatile semiconductor memorydevice in accordance with the first embodiment is described withreference to FIG. 12. As shown in FIG. 12, this second erase operationdiffers from the first erase operation in having source line SL2, drainside select gate lines SGD2,1-SGD2,k, and source side select gate linesSGS2,1-SGS2,k raised to a voltage V1 (=5 V) at time t11.

The above-described voltage V1 causes a voltage applied to the gateinsulating layer of source side select transistors SSTr and drain sideselect transistors SDTr in unselected memory block BK_2 during theabove-described second erase operation to be lower than that during thefirst erase operation. The second erase operation therefore may suppressdamage to the source side select transistors SSTr and drain side selecttransistors SDTr even if those transistors have a low breakdown voltage.

Second Write Operation

Next, a second write operation in the nonvolatile semiconductor memorydevice in accordance with the first embodiment is described withreference to FIG. 13. Now, as shown by the symbol “W11” in FIG. 8A, thefirst write operation executes a charging process for charging the bodyof memory transistors MTr1-MTr4 in memory blocks BK_1 and BK_2 to thepower supply voltage Vdd. In contrast, the second write operation omitsfrom the first write operation this charging process of the body to thepower supply voltage Vdd. That is, as shown in FIG. 13, in the secondwrite operation, at time t21, the source side select gate linesSGS1,1-SGS1,k and SGS2,1-SGS2,k are retained at 0 V. Even in such asecond write operation, prior to execution of the second writeoperation, drain side select gate line SGD1,2 rises from 0 V to Vdd+Vt,whereby the body of the cell unit MU connected to bit lines BL appliedwith the power supply voltage Vdd are charged to the power supplyvoltage Vdd to be set to the floating state, and a similar writeoperation can be executed.

Second Read Operation

Next, a second read operation in the nonvolatile semiconductor memorydevice in accordance with the first embodiment is described withreference to FIG. 14. In the second read operation, the voltage appliedto gates of memory transistors MTr1,2,4 in selected cell unit sMU andthe voltage applied to the gate of selected memory transistor sMTr3differ from those of the first read operation. That is, as shown in FIG.14, at time t31, the word line WL3 is retained at 0 V, and word linesWL1, WL2, and WL4 are raised to read voltage Vread.

Method of Manufacturing

Next, a method of manufacturing the nonvolatile semiconductor memorydevice in accordance with the first embodiment is described withreference to FIGS. 15-18.

First, as shown in FIG. 15, the source side select transistor layer 20,memory transistor layer 30, and drain side select transistor layer 40are formed. Now, an upper portion of the drain side hole 42 is notfilled but left as is.

Next, as shown in FIG. 16, the ohmic contact layer 51 is deposited on anupper portion of the drain side columnar semiconductor layer 44 in thedrain side hole 42. Subsequently, as shown in FIG. 17, the P typesemiconductor layer 52 is deposited on an upper portion of the ohmiccontact layer 51 in the drain side hole 42. Then, as shown in FIG. 18,the N type semiconductor layer 53 is deposited on an upper portion ofthe P type semiconductor layer 52 in the drain side hole 42. The N typesemiconductor layer 53 is formed, for example, by depositing polysiliconand then implanting N+ ions in the polysilicon.

Second Embodiment Configuration

Next, a circuit configuration of a memory cell array 1 included in anonvolatile semiconductor memory device in accordance with a secondembodiment is described with reference to FIG. 19. As shown in FIG. 19,the second embodiment differs from the first embodiment in having thediode DI provided such that its forward bias direction is from the bitline BL side to the drain side select transistor SDTr side. Note that inthe second embodiment, identical symbols are assigned to configurationssimilar to those of the first embodiment, and descriptions thereof areomitted.

The above-described circuit configuration of the nonvolatilesemiconductor memory device is realized by a stacking structure shown inFIG. 20. FIG. 20 is a cross-sectional view of the nonvolatilesemiconductor memory device in accordance with the second embodiment.

As shown in FIG. 20, a configuration of a diode 50 a in the secondembodiment differs from that of the first embodiment. The diode 50 aincludes an N type semiconductor layer 54 and a P type semiconductorlayer 55. The N type semiconductor layer 54 is formed in a column shapeto extend in the stacking direction from the upper surface of the drainside columnar semiconductor layer 44. The P type semiconductor layer 55is formed in a column shape to extend in the stacking direction from anupper surface of the N type semiconductor layer 54. In addition, the Ptype semiconductor layer 55 is formed to have its upper surface incontact with a lower surface of the bit layer 61. The N typesemiconductor layer 54 is configured by polysilicon doped with an N typeimpurity, and the P type semiconductor layer 55 is configured bypolysilicon doped with a P type impurity.

Erase Operation

Next, an erase operation in the nonvolatile semiconductor memory devicein accordance with the second embodiment is described with reference toFIG. 21.

As shown in FIG. 21, in the erase operation of the second embodiment, itis only in the vicinity of gates of source side select transistors SSTrin memory block BK_1 that the GIDL current is generated (refer to symbol“E21”); in the vicinity of gates of drain side select transistors SDTrin memory block BK_1, occurrence of the GIDL current is prohibited. Theerase operation in the second embodiment differs in this regard from theerase operation in the first embodiment. Furthermore, the secondembodiment includes a diode DI connected in a reverse direction to thatof the first embodiment. This may suppress the current flowing fromselected memory block BK_1 into bit line BL1 (refer to symbol “E22”).Consequently, no leak current flows in memory block BK_2. The aboveallows the erase operation in the second embodiment to suppressincorrect erase in unselected memory block BK_2.

As shown in FIG. 22, in contrast to the first embodiment, when executingthe above-described erase operation, at time t11, bit line BL1 isretained at 0 V, and drain side select gate lines SGD2,1-SGD2,k andsource side select gate lines SGS2,1-SGS2,k are retained at 0 V.

Write Operation

Next, a write operation in the nonvolatile semiconductor memory devicein accordance with the second embodiment is described with reference toFIGS. 23A and 23B.

In FIGS. 23A and 23B, an example is described assuming write to beperformed on memory transistor MTr3 in selected cell unit sMU in memoryblock BK_1.

The write operation in the nonvolatile semiconductor memory device inaccordance with the second embodiment is similar to that of the firstembodiment in having the voltage applied to bit line BL1 set to 0 V orthe power supply voltage Vdd (=1.2 V). However, as shown in FIG. 23A,prior to start of the write operation, it has source line SL1 appliedwith a negative voltage −VSG, and differs from the first embodiment inthis respect.

Source side select transistors SSTr in memory block BK_1 are appliedwith 0 V at their gates, whereby the body of cell units MU in memoryblock BK_1 is once charged to the negative voltage −VSG.

On the other hand, drain side select transistors SDTr in memory blockBK_1 are applied with −VSG from the start at their gates, whereby, whilethe body of cell units MU in memory block BK_1 is being charged to thenegative voltage −VSG, the drain side select transistors SDTr in memoryblock BK_1 are maintained turned off.

Subsequently, in the write operation stage, as shown in FIG. 23B, sourceline SL1 has its potential raised from the negative voltage −VSG to 0 V,and drain side select gate line SGD1,2 connected to selected cell unitsMU is applied with power supply voltage Vdd. This causes a potential ofthe body of selected cell unit sMU to become 0 V or the power supplyvoltage Vdd (floating state) according to the potential applied to bitline BL1. In addition, drain side select gate lines SGD1,1 andSGD1,3-1,k connected to unselected cell units MU in selected memoryblock BK_1 are applied with 0 V, whereby the body of the unselected cellunits MU is charged to 0 V or the power supply voltage Vdd to be set tothe floating state. Hereafter, the write operation on selected memoryblock BK_1 is executed in a similar manner to the first embodiment.

Note that in unselected memory block BK_2, drain side select gate linesSGD2,1-2,k are maintained at 0 V throughout, and source side select gatelines SGS2,1-2,k and source line SL2 are maintained at the power supplyvoltage Vdd throughout.

FIG. 24 shows a specific timing chart of the above-described operation.First, at time t21 in FIG. 24, source line SL1 and drain side selectgate lines SGD1,1-SGD1,k are lowered to the negative voltage −VSG. Thiscauses source side select transistors SSTr in memory block BK_1 to beturned on. Further, the voltage of the body of memory transistorsMTr1-MTr4 included in memory block BK_1 is discharged to the samenegative voltage −VSG as source line SL1. Additionally, at time t21,word lines WL1-WL4 are raised to the pass voltage Vpass.

Next, at time t22, source line SL1 and drain side select gate linesSGD1,1-SGD1,k are raised to 0 V. Subsequently, at time t23, drain sideselect gate line SGD1,2 is raised to voltage Vdd+Vt. This causes thedrain side select transistor SDTr included in selected cell unit sMU tobe turned on, whereby the voltage of the body of memory transistorsMTr1-MTr4 included in selected cell unit sMU becomes 0 V or the powersupply voltage Vdd (floating state).

Then, at time t24, word line WL3 is raised to the program voltage Vprog.This causes the write operation on selected memory transistor sMTr3 tobe executed.

Read Operation

A read operation in the nonvolatile semiconductor memory device inaccordance with the second embodiment is similar to that of the firstembodiment, and description thereof is thus omitted.

Third Embodiment Configuration

Next, a stacking structure of a nonvolatile semiconductor memory devicein accordance with a third embodiment is described with reference toFIG. 25. Note that in the third embodiment, identical symbols areassigned to configurations similar to those of the first and secondembodiments, and descriptions thereof are omitted.

As shown in FIG. 25, the third embodiment includes a diode layer 50 bhaving a stacking structure substantially similar to that of the firstembodiment. The diode layer 50 b further includes a P type semiconductorlayer 56 configured to extend in a column shape in the stackingdirection from the upper surface of the N type semiconductor layer 53.This structure allows a bi-directional diode to be formed as the diodeDI.

Fourth Embodiment Configuration

Next, a stacking structure of a nonvolatile semiconductor memory devicein accordance with a fourth embodiment is described with reference toFIG. 26. Note that in the fourth embodiment, identical symbols areassigned to configurations similar to those of the first through thirdembodiments, and descriptions thereof are omitted.

As shown in FIG. 26, the fourth embodiment includes a diode layer 50 chaving a stacking structure substantially similar to that of the secondembodiment. The diode layer 50 c further includes an N typesemiconductor layer 57 configured to extend in a column shape in thestacking direction from the upper surface of the P type semiconductorlayer 55. This structure allows a bi-directional diode to be formed asthe diode DI.

Fifth Embodiment

Next, a stacking structure of a nonvolatile semiconductor memory devicein accordance with a fifth embodiment is described with reference toFIG. 27. Note that in the fifth embodiment, identical symbols areassigned to configurations similar to those of the first embodiment, anddescriptions thereof are omitted.

The nonvolatile semiconductor memory device in accordance with the fifthembodiment differs greatly from the above-described embodiments inincluding a U-shaped memory semiconductor layer 84 shown in FIG. 27 inplace of the I-shaped memory columnar semiconductor layer 34 of theabove-described embodiments.

As shown in FIG. 27, the nonvolatile semiconductor memory device inaccordance with the fifth embodiment includes, stacked sequentially onthe semiconductor substrate 10, a back gate layer 70, a memorytransistor layer 80, a select transistor layer 90, a diode layer 100,and a wiring layer 110. The memory transistor layer 80 functions as thememory transistors MTr. The select transistor layer 90 functions as thedrain side select transistor SDTr and as the source side selecttransistor SSTr. The diode layer 100 functions as the diode DI. Thewiring layer 110 functions as the source line SL and as the bit line BL.

The back gate layer 70 includes a back gate conductive layer 71, asshown in FIG. 27. The back gate conductive layer 71 is formed to extendtwo-dimensionally in the row direction and the column direction parallelto the substrate 10. The back gate conductive layer 71 is configured bypolysilicon (poly-Si).

The back gate layer 70 includes a back gate hole 72, as shown in FIG.27. The back gate hole 72 is formed to dig out the back gate conductivelayer 71. The back gate hole 72 is formed in a substantially rectangularshape having the column direction as a long direction as viewed from anupper surface. The back gate holes 72 are formed in a matrix in the rowdirection and the column direction.

The memory transistor layer 80 is formed in a layer above the back gatelayer 70, as shown in FIG. 27. The memory transistor layer 80 includesword line conductive layers 81 a-81 d. Each of the word line conductivelayers 81 a-81 d functions as the word line WL and as the gate of thememory transistor MTr.

The word line conductive layers 81 a-81 d are stacked sandwichinginterlayer insulating layers. The word line conductive layers 81 a-81 dare formed extending with the row direction as a long direction andhaving a certain pitch in the column direction. The word line conductivelayers 81 a-81 d are configured by polysilicon (poly-Si).

The memory transistor layer 80 includes a memory hole 82, as shown inFIG. 27. The memory hole 82 is formed to penetrate the word lineconductive layers 81 a-81 d and the interlayer insulating layers. Thememory hole 82 is formed to align with a near vicinity of an end of theback gate hole 72 in the column direction.

Moreover, the back gate layer 70 and the memory transistor layer 80include a memory gate insulating layer 83 and a memory semiconductorlayer 84, as shown in FIG. 27. The memory semiconductor layer 84functions as a body of the memory transistors MTr (memory string MS).The memory gate insulating layer 83 includes a charge storage layerconfigured to store a charge, similarly to the above-describedembodiments.

The memory semiconductor layer 84 is formed to fill the back gate hole72 and the memory hole 82. The memory semiconductor layer 84 is formedin a U shape as viewed from the row direction. The memory semiconductorlayer 84 includes a pair of columnar portions 84 a extending in theperpendicular direction with respect to the substrate 10, and a joiningportion 84 b configured to join lower ends of the pair of columnarportions 84 a. The memory semiconductor layer 84 is configured bypolysilicon (poly-Si).

Expressing the above-described configuration of the back gate layer 70in other words, the back gate conductive layer 71 is formed to surroundthe joining portion 84 b with the memory gate insulating layer 83interposed therebetween. Moreover, expressing the above-describedconfiguration of the memory transistor layer 80 in other words, the wordline conductive layers 81 a-81 d are formed to surround the columnarportions 84 a with the memory gate insulating layer 83 interposedtherebetween.

The select transistor layer 90 includes a source side conductive layer91 a and a drain side conductive layer 91 b, as shown in FIG. 27. Thesource side conductive layer 91 a functions as the source side selectgate line SGS and as the gate of the source side select transistor SSTr.The drain side conductive layer 91 b functions as the drain side selectgate line SGD and as the gate of the drain side select transistor SDTr.

The source side conductive layer 91 a is formed in a layer above one ofthe columnar portions 84 a configuring the memory semiconductor layer84. The drain side conductive layer 91 b is in the same layer as thesource side conductive layer 91 a and formed in a layer above the otherof the columnar portions 84 a configuring the memory semiconductor layer84. The source side conductive layer 91 a and the drain side conductivelayer 91 b are formed in stripes extending in the row direction andhaving a certain pitch in the column direction. The source sideconductive layer 91 a and the drain side conductive layer 91 b areconfigured by polysilicon (poly-Si).

The select transistor layer 90 includes a source side hole 92 a and adrain side hole 92 b, as shown in FIG. 27. The source side hole 92 a isformed to penetrate the source side conductive layer 91 a. The drainside hole 92 b is formed to penetrate the drain side conductive layer 91b. The source side hole 92 a and the drain side hole 92 b are eachformed at a position aligning with the memory hole 82.

The select transistor layer 90 includes a source side gate insulatinglayer 93 a, a source side columnar semiconductor layer 94 a, a drainside gate insulating layer 93 b, and a drain side columnar semiconductorlayer 94 b, as shown in FIG. 27. The source side columnar semiconductorlayer 94 a functions as a body of the source side select transistorSSTr. The drain side columnar semiconductor layer 94 b functions as abody of the drain side select transistor SDTr.

The source side gate insulating layer 93 a is formed with a certainthickness on a side surface of the source side hole 92 a. The sourceside columnar semiconductor layer 94 a is formed in a column shape toextend in the perpendicular direction with respect to the substrate 10and to be in contact with a side surface of the source side gateinsulating layer 93 a and one of upper surfaces of the pair of columnarportions 84 a. The source side gate insulating layer 93 a is configuredby silicon oxide (SiO₂). The source side columnar semiconductor layer 94a is configured by polysilicon (poly-Si). The source side columnarsemiconductor layer 94 a has a lower portion 94 aa configured by anintrinsic semiconductor and an upper portion 94 ab configured by an N+type semiconductor.

The drain side gate insulating layer 93 b is formed with a certainthickness on a side surface of the drain side hole 92 b. The drain sidecolumnar semiconductor layer 94 b is formed in a column shape to extendin the perpendicular direction with respect to the substrate 10 and tobe in contact with a side surface of the drain side gate insulatinglayer 93 b and the other of the upper surfaces of the pair of columnarportions 84 a. The drain side gate insulating layer 93 b is configuredby silicon oxide (SiO₂). The drain side columnar semiconductor layer 94b is configured by polysilicon (poly-Si). The drain side columnarsemiconductor layer 94 b has a lower portion 94 ba configured by anintrinsic semiconductor and an upper portion 94 bb configured by an N+type semiconductor.

The diode layer 100 includes a source side ohmic contact layer 101 a, asource side N type semiconductor layer 102 a, a drain side ohmic contactlayer 101 b, a drain side P type semiconductor layer 102 b, and a drainside N type semiconductor layer 103 b, as shown in FIG. 27. The drainside P type semiconductor layer 102 b and drain side N typesemiconductor layer 103 b function as the diode DI.

The source side ohmic contact layer 101 a is formed in a column shapeextending in the stacking direction from an upper surface of the sourceside columnar semiconductor layer 94 a. The source side N typesemiconductor layer 102 a is formed in a column shape extending in thestacking direction from an upper surface of the source side ohmiccontact layer 101 a. The source side N type semiconductor layer 102 a isconfigured by polysilicon including an N type impurity.

The drain side ohmic contact layer 101 b is formed in a column shapeextending in the stacking direction from an upper surface of the drainside columnar semiconductor layer 94 b. The drain side P typesemiconductor layer 102 b is formed in a column shape extending in thestacking direction from an upper surface of the drain side ohmic contactlayer 101 b. The drain side N type semiconductor layer 103 b is formedin a column shape extending in the stacking direction from an uppersurface of the drain side P type semiconductor layer 102 b. The drainside P type semiconductor layer 102 b is configured by polysiliconincluding a P type impurity, and the drain side N type semiconductorlayer 103 b is configured by polysilicon including an N type impurity.

The wiring layer 110 includes a source layer 111, a plug layer 112, anda bit layer 113. The source layer 111 functions as the source line SL.The bit layer 113 functions as the bit line BL.

The source layer 111 is formed to extend in the row direction and to bein contact with an upper surface of the source side N type semiconductorlayer 102 a. The bit layer 113 is formed to extend in the columndirection and to be in contact with an upper surface of the drain side Ntype semiconductor layer 103 b via the plug layer 112. The source layer111, the plug layer 112, and the bit layer 113 are configured by a metalsuch as tungsten.

Method of Manufacturing

Next, a method of manufacturing the nonvolatile semiconductor memorydevice in accordance with the fifth embodiment is described withreference to FIGS. 28-32.

First, as shown in FIG. 28, the back gate layer 70, memory transistorlayer 80, and select transistor layer 90 are formed. Now, an upperportion of the source side hole 92 a and an upper portion of the drainside hole 92 b are not filled but left as is.

Next, as shown in FIG. 29, the source side ohmic contact layer 101 a isdeposited on an upper portion of the source side columnar semiconductorlayer 94 a in the source side hole 92 a. In addition, the drain sideohmic contact layer 101 b is deposited on an upper portion of the drainside columnar semiconductor layer 94 b in the drain side hole 92 b.

Subsequently, as shown in FIG. 30, a source side P type semiconductorlayer 104 is deposited on an upper portion of the source side ohmiccontact layer 101 a in the source side hole 92 a. In addition, the drainside P type semiconductor layer 102 b is deposited on an upper portionof the drain side ohmic contact layer 101 b in the drain side hole 92 b.Next, as shown in FIG. 31, the source side P type semiconductor layer104 in the source side hole 92 a is removed.

Subsequently, as shown in FIG. 32, the source side N type semiconductorlayer 102 a is deposited on the upper surface of the source side ohmiccontact layer 101 a in the source side hole 92 a. In addition, the drainside N type semiconductor layer 103 b is deposited on an upper surfaceof the drain side P type semiconductor layer 102 b in the drain sidehole 92 b. The source side N type semiconductor layer 102 a and drainside N type semiconductor layer 103 b are formed, for example, bydepositing polysilicon and then implanting N+ ions in the polysilicon.

Other Embodiments

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the inventions. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the inventions. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the inventions.

What is claimed is:
 1. A nonvolatile semiconductor memory device,comprising: a plurality of memory blocks, each including a plurality ofcell units and each configured as a smallest unit of an erase operation;a first line provided commonly to the plurality of memory blocks andconnected to one ends of the plurality of cell units; a second lineconnected to the other ends of the plurality of cell units; and acontrol circuit configured to control a voltage applied to the pluralityof memory blocks, each of the plurality of cell units comprising: amemory string configured by a plurality of memory transistors connectedin series, the memory transistors being electrically rewritable; a firsttransistor having one end connected to one end of the memory string; asecond transistor provided between the other end of the memory stringand the second line; and a diode provided between the first transistorand the first line and having a forward bias direction from a side ofthe first transistor to a side of the first line, the memory stringcomprising: a first semiconductor layer including a columnar portionextending in a perpendicular direction with respect to a substrate, thefirst semiconductor layer being configured to function as a body of thememory transistors; a charge storage layer formed to surround a sidesurface of the columnar portion and configured to be capable of storinga charge; and a first conductive layer formed commonly in the pluralityof memory blocks to surround the side surface of the columnar portionwith the charge storage layer interposed therebetween, the firstconductive layer being configured to function as a gate of the memorytransistors, and the diode comprising: a second semiconductor layer of afirst conductivity type, the second semiconductor layer extending in theperpendicular direction with respect to the substrate; and a thirdsemiconductor layer of a second conductivity type, the thirdsemiconductor layer being in contact with an upper surface of the secondsemiconductor layer and extending in the perpendicular direction withrespect to the substrate, the control circuit being configured toperform the erase operation in a selected one of the memory blocks bysetting a voltage of the first line higher than a voltage of a gate ofthe first transistor by a first voltage to generate a GIDL current forraising a voltage of the body of the memory transistors, and setting avoltage of the gate of the memory transistors lower than the voltage ofthe body of the memory transistors by a second voltage, and the controlcircuit being configured to prohibit the erase operation in anunselected one of the memory blocks by setting a voltage differencebetween the voltage of the first line and the voltage of the gate of thefirst transistor to a third voltage different from the first voltage forprohibiting generation of the GIDL current.